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Maintenance Description
Issue 1 December 1997 9-19
Figure 9-5. Unidirectional Line Protection Switching
P P
S
P
S
P
failure
DDM-2000 A
S
P
S
P
DDM-2000 C
S
S
failure
KEY
Active
Standby
All four fibers are operational
Both SERVICE fibers are "Active"
Location C selects the
PROTECTION fiber from
A to C as "Active" fiber
SERVICE fiber from C to A fails
location A detects failure
S
P
S
P
failure
P
P
S S
PROTECTION fiber from
Location A selects the
C to A as "Active" fiber
A to C remains "Active"
Location C detects failure
Both PROTECTION fibers are "Standby"
SERVICE fiber from A to C fails
The PROTECTION fiber from
(a)
(b)
(c)
(d)
(e)
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